having had childhood cancer with radiation treatment and immunosuppression (less common)

Causes

Cancer is caused by mutations of the genetic material (DNA) in a cell. The mutated genes tell the cell to divide and keep dividing, eventually producing an uncontrolled growth of cells with the same mutation. We don't understand the process fully, but we know of many carcinogens, substances that provoke cancer or increase your chance of getting it.

For skin cancer, the primary carcinogen is sunlight. Studies have shown that melanoma is more common among people who have spent a lot of time in the sun. The damage caused by UV light can lead to mutations. The incidence of melanoma is rising, a reflection of the boom in sunbathing since the Second World War.

People of African descent are less likely to get melanoma than Caucasians, though they can get a rare form that appears on mucous membranes (e.g., on the inside of the mouth). Among Caucasians, paler people are more susceptible. The risk goes up with for those with blue or green eyes, fair hair, and freckles.

Most people get the bulk of their sun exposure as children, and people who had severe sunburn before age 18 are at higher risk for skin cancer. Along with UV light from the sun or indoor tanning beds, X-rays have been associated with an increased risk for melanoma, as has exposure to radium or arsenic.

Skin cells called melanocytes provide the brown pigment that results when we tan in the sun. Melanoma always starts in melanocytes. It can take root in existing moles on the skin, which are actually groups of melanocytes, or it can start in a single melanocyte cell in normal skin.

Some moles are more risky than others.Dysplastic nevi are moles that look abnormal in some way and may turn into melanoma in the future. The way to recognize dysplastic nevi is as simple as ABCDE – they will have one or more of the following characteristics:

Asymmetry: The mole is not round like normal moles, but is odd-shaped or elongated.

Border: The border is irregular, like a rugged coastline on a map, and it fades into the skin rather than making a sharp edge.

Colour: The mole has areas of different colour, possibly including white, blue, red, or (especially) black.

Diameter: It is larger than the size of a pencil eraser (or greater than 6 mm).

Symptoms and Complications

Melanoma is a visible kind of cancer, unlike others that start inside the body (such as breast cancer or prostate cancer). Melanoma often causes changes that are visible and apparent. What's important is to recognize the signs and have a doctor check any suspicious moles.

A changing mole doesn't necessarily mean cancer, but it certainly needs looking at. A new mole on previously clear skin is equally significant. See a dermatologist or your family doctor about any of the following changes:

A mole grows, changes colour, becomes raised from the skin, or develops small irregular bumps or crags.

A mole becomes hard, crusty, or irritated, or is bleeding.

An ulcer or cut doesn't heal after a month.

There are black spots under the base of the nails.

There is any new growth or patch of abnormal colour on the skin.

Melanoma is a very dangerous skin cancer if left untreated because it can spread to other parts of the body and can even lead to death.

Making the Diagnosis

Your family doctor or dermatologist can diagnose melanoma. A sample of the tissue is taken from a mole (this is called a biopsy). It's examined in a lab for cancer cells. A biopsy of nearby lymph nodes or other tissue may be done to check if the cancer has spread.

Treatment and Prevention

If you spot melanoma and get it removed early, before it penetrates under the skin, your chance of a cure is close to 100%.

If the melanoma has spread horizontally (i.e., over the surface of the skin), the prognosis is still very good so long as it hasn't penetrated deep under the skin. There are different types of melanoma, but the type is less important to your prospects than the thickness and the degree of penetration.

The way to treat melanoma treatment is to have surgery to remove it as early as possible. This can be quite simple and painless in the early stages, not much worse than removing a wart. If the cancer has spread across the skin, surgery might leave a mark. Even fairly deep melanoma is potentially quite curable if it hasn't affected other organs.

Chemotherapy, radiation, or biological (immunotherapy) therapies may also be recommended depending on the severity and degree of melanoma diagnosed.

Preventing melanoma is all about avoiding too much sun. Sunburns are worst, but even excessive tanning increases the risk of melanoma dramatically. You should always wear plenty of sunscreen (sun protection factor [SPF] 15 or higher) if out in the bright sunshine and reapply it as often as directed. If possible, stay out of the sun when the ultraviolet exposure is at its maximum (i.e., between 10 am and 4 pm). Another recommendation is to wear protective clothing. This means clothing that covers the arms and legs, plus a wide-brimmed hat. Similarly, you should always wear sunglasses that provide protection against both UVA and UVB rays. Remember that UV light can also penetrate clouds, so you should take precautions on cloudy days too. Everyone should avoid tanning beds, as these also increase your risk of melanoma.

We also need to protect kids from the sun. Many kids develop a deep tan every summer and their parents assume that if they're not sunburned there's no problem. Children's skin is always more vulnerable, and these tans add up to a higher risk of skin cancer in later life.

To help detect melanoma early, everyone should perform regular skin self-exams looking for any new or changed moles or skin lesions. If any suspicious areas are found, make an appointment with your doctor as soon as possible for further assessment.